A bolt tightening device is configured in such a manner that a bolt held by a bolt holding portion provided at a forward end of a socket connected to an output shaft of a nut runner is tightened to a work by a rotation of the socket caused by an action of the nut runner.
According to a conventional case in which a plurality of bolts are tightened by using one nut runner, the following two steps are repeated. In the first step, the nut runner is moved to a place where the bolt is supplied and then the bolt is supplied to a bolt holding portion provided at a forward end portion of a socket connected to an output shaft of the nut runner. In the second step, the nut runner is moved to a work side and the bolt held by the bolt holding portion is tightened to the work. According to this method, each time one bolt is tightened, the nut runner must be reciprocated from the work side to the bolt supplying place. Therefore, an efficiency is deteriorated. In this connection, it is possible to enhance the efficiency by using a plurality of nut runners. However, when a plurality of nut runners are provided, the equipment investment is increased.
Moreover, the following bolt tightening device is known.
The bolt tightening device includes: a slider which advances in a work direction together with a nut runner and stops at a predetermined position; and a bolt catcher pivotally supported by the slider. Concerning this bolt tightening device, for example, refer to Patent Document 1. In this bolt tightening device, a bolt is dropped from an upper portion of the bolt catcher through a pipe and then the bolt catcher is rotated so that the bolt can be concentric with a socket of the bolt runner. When the nut runner is advanced to the work direction under this condition, the socket is inserted into the bolt catcher so as to deliver the bolt to the socket.    [Patent Document 1] JP-A-64-078730
When this bolt tightening device is used, it becomes unnecessary to move the nut runner to the bolt supply portion, which is apart from the work, after a completion of tightening the bolt. Accordingly, the efficiency can be enhanced. However, in this bolt tightening device, an auxiliary device for supplying a bolt, which includes a slider and a bolt catcher, is arranged in the neighborhood of the forward end of the socket of the nut runner. Therefore, this auxiliary device interferes with the work and it becomes impossible to tighten the bolt.